Conventional vehicle ignition systems include a switch operated by a key to connect the vehicle battery to the ignition coil. This arrangement is not very secure, and thieves have been able to energize the vehicle engine by short-circuiting the switch operated by the key.
Additional vehicle security systems have been proposed, independent of the ignition system, for example causing an alarm to sound if the vehicle is tampered with, but if the alarm is itself disabled, it is still possible to dive away the vehicle by short-circuiting the ignition switch.